1. Technical Field
Example embodiments of the present invention relate to device-to-device communications, and more particularly, a device-to-device communication method, a mobile device using the same, and a device-to-device communication control method.
2. Related Art
Recently, as the use of applications for smart phones, etc. that wirelessly transmit and receive large amounts of data while moving has been increasing, overhead frequency of mobile communications networks has been rapidly increasing, and resulting problems of network failure and service quality degradation have been becoming more serious day by day.
As one solution, technology for providing device-to-device communication between adjacent devices located in the same cell or neighboring cells within a radius of one to two km in a mobile communications system is being considered.
Device-to-device communication (hereinafter referred to as “D2D communication”) refers to a communication method in which direct data transmission and reception between two adjacent terminals are performed without a base station. That is, D2D communication technology sets a D2D wireless link through a mobile communication wireless interface using a mobile communication frequency band between adjacent devices, and then directly exchanges data between the devices through the D2D wireless link without a base station.
Such D2D technology provides an increased transmission rate for users located at a cell boundary without increased infrastructure costs, supports cellular network access for devices out of a service area, and aims to increase system capacity by decreasing interference.
Conventional technology, for example, WiFi Direct, Bluetooth, and Zigbee, only supports communication between devices within several hundred meters. However, D2D communication technology enables direct communication between devices located within a radius of one to two km based on long- and mid-range transmission capability provided by a mobile communications wireless interface. The D2D technology in a cellular mobile communications system has advantages such as wider cell coverage and tighter security than conventional technology such as WiFi Direct, Bluetooth, and Zigbee, and thus its importance is being highlighted and it is being standardized in 3GPP.
D2D communication technology has some additional advantages. Since communication between adjacent devices is performed without passing through a network, it is possible to reduce a load of the network. When adjacent devices located at a cell boundary communicate with each other via a base station, only low-speed data transmission is possible. However, when devices communicate directly, high-speed data transmission is possible due to a significantly improved signal environment between adjacent devices. As a result, it is possible to provide users with service with improved performance.
In addition, when adjacent devices located at a cell boundary communicate via a base station, it is necessary for each device to maintain high enough transmission power to reach the base station. However, when devices communicate directly, transmission power can be significantly decreased and battery life can be increased.
However, when retransmission is necessary due to unsuccessful data transmission, since control information needs to be exchanged via the base station, there is a problem in that a control load increases in device-to-device communication when retransmission is performed.